Method of making bottle caps



y 17, J, PARKER 1,858,279

METHOD OF MAKING BOTTLE CAPS Filed March 27, 1930 u I, I I I, I w l 11-I '1 H n I I flNVENT BWQ/ k ATTORNEY- Patented May 17, 1932 UNITEDSTATES PATENT OFFICE CECIL J". PARKER, OF GOVANS, MARYLAND, ASSIGNOR TOCROWN CORK & SEAL COM- PANY, INC., NEW YORK, N. Y., A CORPORATION OF NEWYORK v METHOD OF MAKING BOTTLE CAPS Application filed March 27, 1930.Serial No. 439,302.

My invention relates to a method of making bottle caps, and moreparticularly to the production of caps of the type which embodiestherein a skirted metal shell having an annular gasket within the shelladjacent the skirt.

Heretofore, in the production of caps of the type to which my inventionrelates, two practices have been followed. In producing these caps byone of the old methods, rings of soft vulcanized rubber were firstformed, and these rings were secured in position in the shell by meansof cement or other adhesive. By the other method, caps were produced byflowing a semi-plastic composition of latex and a mineral filler into achannel formed in the top of the shell, the material being allowed toset under normal factory temperatures or gentle heat.

In the former of these methods, the procedure in producing the gasketsand in applying them to the metal shell was costly in the light of thelow cost, of the completed product. The latter, method resulted in a capwhich was not suitable for use in the closure of containers which, afterbeing capped, had to be subjected to high temperatures for the purposeofsterilization, or the cooking of the contents. Furthermore, a cap ofthis character could not be effectively used when the pressure developedwithinIa container exceeds 75 or 80 pounds per square inch, irrespectiveof whether this pressure was developed as a result of the subjecting ofthe container to heat, or from the separation of carbonic acid gas fromthe contents of the bottle due to other reasons.

With the above conditions in mind, I have developed a method of makingbottle caps by which the cost of production of such caps may be verymuch cheapened as compared to the cap having the vulcanized ringcemented within same, and which will form an effective seal irrespectiveof the pressure developed within the container, or of the temperature towhich same may be subjected after the cap has been applied thereto.

In the practice of the method of my invention, I secure the bonding ofthe gasket 50 to the metal shell without the employment of a stratum ofadhesive between the gasket and the shell, utilizing the adhesivenessinherent to the rubber compound forming the gasket during vulcanizationto secure the gasket in position within the shell. v

By the method of my invention I am also enabled to provide a cap whereinthe gasket possesses a sufficiently permanent set to ensure an effectivesealing action and yet have the gasket free of any uncombinedvulcanizing agent which can impart the characteristic flavor of softvulcanized rubber to the contents of the container, or have anydeleterious action thereon.

My invention contemplates not only the employment of a rubber compoundhaving special characteristics for facilitating the production of agasket having the desired properties, but one which will expedite theproduction of the cap as a whole While securing an adequate bondingaction between the gasket and the metal shell.

The invention consists primarily in a method of making bottle capsembodying therein the extrusion in tubular or annular form of a compoundcontaining rubber, a filler, and a low content of a vulcanizing agent,the separation of the tube, in its unvulcanized condition, into rings,the delivery of such rings to a skirted metallic shell within andadjacent the skirt thcreof,.and the subjection of the metallic shell andits contained ring to a vulcanizing temperature, whereby said ring willbe bonded to the metal shell and will be simultaneously semi-vulcanized;and in i such other novel steps and practices as are I hereinafter setforth and described, and more particularly pointed out in the claimshereto appended.

Referring to the drawings,

Fig. 1 is a conventional showing of an ordinary tubing machine;

Fig. 2 is a section of a completed bottle cap made by the method of theinvention; and

Fig. 3 is a perspective View of one of the gasket forming rings, priorto its application to the metallic shell.

Like letters refer to like parts throughout the several views.

In the practice of the method of my-invention, I form a rubber compoundcontaining ordinary commercial rubber, a filler of any desired type wellknown to workers in the rubber making art, a vulcanizing agent,preferably sulfur, the proportion of which to the rubber content of thebatch is very much lower than that heretofore used in the rubber makingart, and an accelerator, preferably an organic, rapid acting acceleratorsuch as tetra-methyl-thiuram-disulphide.

While generally, in the rubber art, the amount of sulfur used to securea soft vulcanized product is 3% or more, in the compound above referredto I use only approximately 1% of the rubber content of the batch, thusavoiding any possibility of free or uncombined sulfur in the completedgasket. This compound is produced by the methods usually employed by therubber maker, the invention relating more particularly to the method ofproducing a bottle cap, having certain desirable and novel properties,resulting in part from the character of the compound used in the gasket,and in part from the practices followed in assembling gaskets of thiscompound in the cap structure.

A compound of the character above described is given the desired formand dimensions according to the size and character of the shell of thecap of which it is to form a part, in any desired manner, as by means ofa tubing machine as shown at a in the drawings. Ordinarily, a ringgasket is employed.

The material extruded by the machine a is of a thickness to ensuresufiicient body in the gasket. Such a gasket of the ring type is shownat I; in Fig. 3 of the drawings, the tube from which it is out beingshown at 0 in Fig. 1. The material of the gasket 7), when cut from thetubing, is plastic.

This gasket is placed in the shell (1 of the cap adjacent the skirtthereof. In the drawings, I have shown the invention in connection witha metal shell of the crown type in which the skirt is fluted tofacilitate the attachment of the cap to the bottle or other container.Ordinarily, such shells have a lacquer coated inner surface,-which ishighly desirable as facilitating bonding action between the gasket andthe shell, irrespective of the character of the gasket used.

The plastic, pre-formed gasket 1) is deposited directly upon the innersurface of the shell, or upon the lacquer coating, when such is used,and adheres: thereto without the necessity for the use of any adhesivebetween the gasket and the shell. Subsequently, the shell with itscontained gasket is subjected to a temperature of approximately 240 F.for a sufficient interval to effectively cure the material of the gasketand to give permanency to the bond between same and the metal shell.

The content of the vulcanizing medium, while sub-normal as known to therubber making art, is adequate to give the gasket a proper set andresiliency adequate to secure an effective sealing action when the capis applied to a bottle or other container. The low sulfur content,however, will avoid any possibility of the presence, in the gasket ofthe completed cap, of free or uncombined sulfur or its presence insufficient volume to impart any of the characteristic tastes of ordinaryrubber having sulfur as a vulcanizing medium, to the contents of abottle or other container closed by the cap of my invention.

The use of an accelerator permits an approximate control of the timeinterval, and from a manufacturing standpoint expedites the productionof the caps with a minimum of wastage.

The character of the compound used, and the manner of forming andassembling the gasket in the shell permits the production of the capwith as few steps as is practicable while resulting in a productincluding therein a soft vulcanized rubber gasket bonded directly to thematerial of the shell.

When using a ring gasket, it is preferable to employ a shell (Z, havingformed in the top thereof a channel 6 adapted to receive the gasket, theplastic material of the gasket readily conforming to this channelfollowing the seating of the gasket therein and during the vulcaizationstage.

It is not my intention to limit the invention to the particularconfiguration or dimensions of the gasket or of the shell, nor is it myintention to limit myself to any particular rubber compound, with theexception that the content of the vulcanizing medium must be so low asto approximate 1% of the rubber content of the batch.

It is also essential to the invention that the packing gasket shall beapplied to the shell while the material thereof is plastic, and that theshell with its contained gasket shall be subjected to the requiredvulcanizing temperature.

Having described the invention, what I claim as new and desire to haveprotected by Letters Patent, is

1. A method of making bottle caps embodying therein the extrusion intubular form of a compound containing rubber, a filler, and a lowcontent of a vulcanizing agent, the separation of the tube, in itsunvulcanized condition, into rings, the delivery of such rings to askirted metallic shell Within and adjacent the skirt thereof, and thesub vulcanizing agent, the separation of the ex- 4 truded compound intogasket sections of the desired thickness, the deposit of a section whilein an unvulcanized condition in a. skirted metallic shell, and thesubjection of the metallic shell and its contained gasket section to avulcanizing temperature, whereby said gasket will be bonded to the metalshell and will be simultaneously semi-vulcanized.

3. A method of making bottle caps embodying therein the extrusion intubular form of a compound containing rubber, a filler, a low content ofa vulcanizing agent, and an organic accelerator, the separation of thetube, in its unvulcanized condition, into rings, the delivery of suchrings to a skirted metallic shell within and adjacent the skirt thereof,and the subjection of the metallic shell and its contained ring to avulcanizing temperature, whereby said ring will be bonded to the metalshell and will be simultaneously semi-vulcanized.

4. A method of making bottle caps embodying therein the extrusion in aform to enter a bottle cap of a compound containing rubber, a filler,approximately 1% of a vulcanizing agent, and an organic accelerator, theseparation of the extruded compound into gasket sections of the desiredthickness, the deposit of a section while in an nnvul canized conditionin a skirted metallic shell, and the subjection of the metallic shelland its contained gasket section to a vulcanizin temperature, wherebysaid gasket will be bonded to the metal shell and will be simultaneouslysemi-vulcanized.

In witness whereof I have hereunto aflixed my signature.

CECIL J. PARKER.

